An ion chromatograph introduces a sample into a separation column and separates the sample into component ions, and then, guides an eluate from the separation column into an electrical conductivity meter cell and detects the electrical conductivity, to thereby detect component ions. At this time, in order to reduce the electrical conductivity of the eluate by removing nontarget ions in the eluate from the separation column and to enable highly sensitive measurement, a suppressor is arranged between the separation column and a detector (see Patent Document 1).
As general suppressors, those that suppress the electrical conductivity of the eluate by a column filled with ion-exchange resin as a filler, and those that suppress the electrical conductivity of the eluate by arranging an eluate path and a regenerant path that face each other across an ion exchange film, and causing an eluate and a regenerant to flow through the paths are known. However, these suppressors have the following problems.
First, the electrical conductivity meter is very sensitive to temperature, and thus, there is a problem that an electrical conductivity signal changes even by a slight variation in the temperature of liquid that is introduced into the cell or the ambient temperature, appearing as a noise in the chromatogram.
Also, since the detection sensitivity is determined by the S/N ratio, the detection sensitivity is increased to the extent that the noise is smaller, even if the output signal of the detector with respect to the density is the same. The degree of change in the electrical conductivity by the temperature is greater as the electrical conductivity of liquid is higher. In the case of an ion chromatograph, in order to separate an ionic sample using a separation column containing ion-exchange resin, a highly ionic eluate is indispensable, and as a result, the electrical conductivity of the eluate is increased. Accordingly, although the electrical conductivity of the eluate from the column, that is, background electrical conductivity, is suppressed by the suppressor, it is not possible to completely eliminate the background electrical conductivity. Accordingly, there is a problem that, when the temperature of the suppressor changes due to a change in the ambient temperature of the suppressor, the temperature of the eluate from the suppressor also changes, and the background electrical conductivity of the eluate is changed under the influence, and the measurement accuracy is reduced.